(a) Field of the Invention
The present invention relates to methods and apparatus for measuring the power or amplitude densities of the spectral components of a digital signal comprising a sequence of numbers x(nT), where T is the sampling period and n is the rank of the sample. The technique disclosed applies to either signals naturally limited in time of interval .rho.=NT, or signals of unlimited duration previously subjected to temporal filtering of interval .rho..
(b) Discussion of the Prior Art
Known procedures for measuring the power spectral density of digital signals most often use methods which are based on either selective filtering, followed by quadratic integration, or on a calculation of the discrete Fourier transform (DFT) of the signal to be analyzed. The major disadvantage of these latter methods--apart from the complexity of implementation when N is large--is that they allow analysis of the spectrum only for frequencies which are multiples of 1/NT.